Clamp-like sheet metal nut with centering strip

ABSTRACT

A clamp-style sheet metal nut having a self-centering strip. The nut has two legs resiliently spaced apart. One leg has a threaded boss, the other leg has a through-bore for accepting the thread fastener. The self-centering strip is formed by twisting an annular strip of metal cut from the second leg and supported by a pair of resilient arms. The self-centering strip forms a circular aperture for accepting the threaded member and extends up into the bore of the carrier plate.

BACKGROUND OF THE INVENTION

It is known to connect material to a carrier plate using a clamp-typesheet metal nut which is slipped onto a carrier plate. The sheet metalnut consists of two legs, connected to each other, with a pretappedplunged boss in one leg and a through-bore for a screw in the other leg.An annular centering strip is formed around at least three-fourths ofthe circumference of the through-bore; the rear region of the centeringstrip bends diagonally upward towards the threaded leg.

This type of slip-on nut is used for connecting a carrier plate, such asan auto body of a motor vehicle, to another component or sheet. Thecentering strip offers the advantage that the threaded portion of thesheet metal nut, when the former is being slipped on, is fixed preciselyover the fastening hole of the carrier plate. When driving in the screw,the sheet metal nut no longer must be held, which means that assembly isgreatly facilitated, particularly when the fastening hole is difficultto access.

If the sheet metal of the carrier plate is coated with a protectivecoating, e.g., a lacquer coating, then it should not be damaged by thefastening process. Therefore it is important that, as the sheet metalnut is being slipped on, the centering strip be able to spring backsoftly and, in this connection, without spring into the hole of theclamping leg from which the centering strip has been cut without damage.In order to fulfill said requirement, the centering strip in the priorart of the invention, in accordance with DE 2,828,078 C2, is cut suchthat it is surrounded by a region which has been cut free. However, theclamping leg must be of a wider design for the free punch, and requiresa correspondingly wider sheet metal strip as starting material. Inaddition, the increased leg width may become an obstacle for narrowspatial conditions.

SUMMARY OF THE INVENTION

The purpose of the invention is to fashion a centering strip for thesheet metal nut such that with equally good spring-back properties thefree punch may be largely omitted, and therefore less sheet metalmaterial is required to produce the sheet metal nut.

The problem is solved in accordance with the present invention by thefact that a centering strip after it has been cut in, is bent 90° overits entire length consequentlyextending perpendicularly to the plane ofthe clamping leg. This results in an advantageous deeper entry of thecentering strip into the fastening hole of the carrier plate,consequently yielding an improved centering effect. In addition, theouter diameter of a "on edge" centering strip is less than the outerdiameter of a conventional centering strip which lays flat, such thatthe through-bore in the carrier plate may also be of a smaller design,corresponding with the smaller outer diameter of the centering strip.

The advantages of the invention become especially apparent in thecentering ring formation in which the centering strip is connected tothe clamping leg by means of two parallel strips which spring backgently, and the outer edge of the centering strip is turned to an "onedge" position between the connecting elements.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing represents an embodiment of a sheet metal nut in accordancewith the invention which will be explained in greater detail in thefollowing. Shown are:

FIG. 1: Shown is a side view of a clamp-type sheet metal nut,

FIG. 2: Shown is a horizontal sectional view taken through the sheetmetal nut between the two legs, taken along line II--II of FIG. 1,

FIG. 3: Shown is a sectional view taken through the clamping leg inaccordance with line III--III of FIG. 2, and

FIG. 4: Shown is the sheet metal nut, premounted on a carrier plate, inthe centering position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The sheet metal nut (15) represented in the FIGS. 1-4 consists of twoC-shaped legs (1,2) connected to each other, with one leg (1) providedwith a screw thread (3) in a boss (8) and the other leg (2) providedwith a through-bore (4) for a screw (not shown) to be screwed into thethread (3).

In this regard, the thread bearing leg (1) is provided with an angledlead-in leg portion (5), which opens for sliding on to the carrier platein the direction (A). In the present embodiment, the leg (1) isconnected to the other clamping leg (2) by means of two elasticspring-back elements (6) and a transverse wall (7). This makes itpossible for the thread bearing leg (1) to always lie flat on thecarrier plate (11) when the sheet metal nut is slipped onto carrierplates of differing thicknesses.

The screw thread (3) is located in the tapped boss (8), which is formedon the thread bearing leg (1) using the known deep-draw method.Alternatively, a pretapped plunge boss having only one thread (3), forscrewing in a sheet metal screw, may be provided in lieu of a tappedboss (8).

A centering strip (9) is formed on the clamping leg (2), around thethrough-bore (4), to extend around at least three-fourths of thecircumference of the hole. The centering strip is connected to theclamping leg (2) by means of two parallel arms (10), such that itsprings back gently. The centering strip has a rear region, when viewedin the slip-on direction "A", which bends upward toward the threadbearing leg (1). When a sheet metal nut is being slipped onto a carrierplate (11), (compare FIG. 4), said centering strip (9) serves to fix thesheet metal nut precisely over a fastening hole (12) of the carrierplate. The centering strip (9) initially yields to the plane of theclamping leg (2) and then springs back into the fastening hole (12) andlocks in there.

As evident, in particular, from FIGS. 2 and 3, the entire length of thecentering strip (9) is bent 90° with respect to the plane of the leg(2), with it being preferable to set the outer edge (13) of thecentering strip "on edge". This results in a small distance "a" betweenthe strip (9) and the cut edge (14) formed in the clamping leg (2)formed from stamping out the centering strip (9). This results in theadvantage that the centering strip (9) may also deflect to the plane ofthe clamping leg (2), as in the prior art, but without a free punch.

To fabricate the clamp, a twisting or bending of the centering strip (9)into the "on edge" position may be achieved by simple means, such asplacing a female mold under the strip (9). The inner diameter of thefemale mold is smaller than the outer diameter of a stamped out strip(9) which is still lying flat. The strip (9) is then pressed into saidfemale mold with a stamp. The outer diameter of the stamp is somewhatgreater than the inner diameter of a strip (9) when it is lying flat.The intermediate space between the stamp and female mold should beapproximately equal to the thickness of the sheet metal of the centeringstrip (9), such that the strip (9) when plunged into the female mold isnecessarily bent 90° to the "on edge" position.

I claim:
 1. A clamp-type sheet metal nut for mounting to a carrierplate, said sheet metal nut comprising a pair of spaced legs, one ofsaid legs having a threaded boss and an other of said legs having athrough-bore, said other leg having an outer surface extending on aplane and an annular centering strip formed around the through-bore andextending around at least three-fourths of the circumference of thethrough-bore, the centering strip having an inner surface extending inan axial direction around the through-bore to a pair of twisted endportions twisted through an arc of 90° such that the inner surface isbent from the axial direction to extend along the plane of the outersurface.
 2. The clamp-type sheet metal nut of claim 1, furthercomprising a pair of resilient parallel arms extending from the clampingleg to the centering strip.